What are the other Names for this Condition? (Also known as/Synonyms)

• ATN (Acute Tubular Necrosis)
• Renal Failure with Acute Tubular Necrosis
• Renal Tubular Necrosis 

What is Acute Tubular Necrosis? (Definition/Background Information)

The important functions of the kidneys are:

• To remove waste substances from the body, which are a by-product of physical and chemical reactions in the body
• To monitor the amount of water in the body
• To maintain the electrolytes at an optimal level
• To make hormones that help in the production of red blood cells, regulate blood pressure, and to keep the bones healthy

The basic functional unit of the kidney is the nephron. It can be divided into two major parts:

• Renal corpuscle: It is made up of glomerulus (network of capillaries) surrounded by glomerular capsule (hollow space). The waste substances move from the glomerulus to the glomerular space to form urine. The urine collected in the glomerular capsule, empties in to the tubules
• Tubules: These are hollow tubes that move urine from the glomerular capsule to the collecting duct. The tubules recover (concentrate urine) non-waste solutes from the urine. Then, the urine passes through collecting duct, renal pelvis, ureter, bladder, and exits the body through the urethra

In acute renal failure (ARF or acute kidney injury), there is a sudden decrease in kidney function, which is characterized by sudden increase in the blood levels of blood urea nitrogen (BUN) and creatinine

• Acute Tubular Necrosis (ATN) is a form of acute kidney injury, in which the cells of the tubule are damaged
• ATN is commonly caused by ischemia (decreased blood flow to the organs and tissues) and toxin exposure. Toxins from outside the body, such as contrast dyes used for imaging purposes, commonly cause more damage than toxins that originate within the body
• Hospitalization, hydration, and supportive measures are important for a favorable outcome 

Who gets Acute Tubular Necrosis? (Age and Sex Distribution)

• Although individuals of any age can be affected by Acute Tubular Necrosis, it is more common in older individuals due to an increased prevalence of associated medical conditions
• Both males and females are affected
• The condition is seen all over the world; there is no particular geographical predominance
• There is no racial or ethnic preference observed

What are the Risk Factors for Acute Tubular Necrosis? (Predisposing Factors)

The risk factors of Acute Tubular Necrosis include:

• Any mechanism or health condition that decreases the volume of blood to the kidneys is a risk factor
• Decreased volume of blood in the body (hypovolemia) either due to blood loss or loss of body fluids. For example:
  • Blood loss due to a motor vehicle accident
  • Blood loss during surgery and inadequate fluid administered to compensate for the loss
• Decreased blood pressure due to any cause, such as due to widespread infection and inflammation in the body and blood (sepsis)
• Any individual taking medication or exposed to chemicals that are toxic to the tubule are at risk:
  • Individuals undergoing an imaging test that uses a dye (contrast) are at risk, because the dye can injure the kidney tubules
  • Other factors that can pose a risk for Acute Tubular Necrosis are antibiotics, such as aminoglycosides, amphotericin B, vancomycin, cephalosporin, and chemotherapy drugs (cyclosporine)
  • Any crush injury during an automobile accident can release myoglobin from the muscle, which are toxic if present in high levels
  • Increased levels of uric acid in blood in individuals due to chemotherapy for cancer are also at risk
• Any individual with chronic kidney disease, diabetes mellitus, or liver disease,  with or without the above risk factors are susceptible to ATN 

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider. 

What are the Causes of Acute Tubular Necrosis? (Etiology)

The causes of Acute Tubular Necrosis can be divided on the basis of the mechanism of injury to the tubular cells.

• Pre-renal causes: These are the causes that refer to events occurring in the blood vessels before entering the kidneys
  • Decreased blood flow or blood pressure to the kidneys, which may be due to severe loss of blood due to trauma; fluid loss due to dehydration, diarrhea, or severe burns
  • Decreased pressure due to excess consumption of blood pressure medications, septic shock (infection) etc.
• Renal causes: These are factors that directly damage the kidney (tubules) and can cause kidney failure. These include medications that can damage the kidney such as:
  • Pain medications such as NSAIDs
  • Blood pressure medications such as ACEIs and ARBs
  • Antibiotics: Aminoglycosides, acyclovir, indinavir, amphotericin B, vancomycin, cephalosporin
  • IV contrast dyes used for imaging purposes
• Certain substances that are toxic to the kidney and can cause ATN include alcohol, cocaine, and heavy metals such as arsenic and cadmium
• Substances produced within the body, if present in high levels, such as myoglobin (due to crush injury of muscle), uric acid (from cell breakdown. when on chemotherapy), hemoglobin, Bence Jones proteins (multiple myeloma), etc., can cause ATN

What are the Signs and Symptoms of Acute Tubular Necrosis?

The signs and symptoms of Acute Tubular Necrosis depend on the severity of the condition. They include:

• Decrease of urine volume and in severe cases, no urine output may be present
• Nonspecific symptoms such as nausea, uneasiness, vomiting, altered perception (sensorium), or confusion
• Increased thirst with loss of appetite
• Decreased formation of urine (oliguria) occurs due to decreased flow of blood to kidneys
• Abdominal pain
• Seizures
• Abnormal bleeding tendency
• Accumulation of waste products, such as ammonia, can cause confusion, loss of consciousness, or even coma
• Various electrolyte imbalances can take place when kidneys are injured: Increased levels of potassium can cause heart conditions, such as irregular heart beat (arrhythmia), and muscle weaknesses

How is Acute Tubular Necrosis Diagnosed?

The following tools may be used to diagnose Acute Tubular Necrosis:

• Thorough evaluation of the individual’s medical history and a thorough physical examination of the skin, heart, abdomen, rectum, and vagina
• A physical examination may reveal:
  • Increase in blood pressure (hypertension)
  • General swelling (edema)
  • Abnormal sounds from the heart (pericardial rub)
  • Abnormal sounds from the lungs (also called rales, due to excess accumulation of fluid in the body)
  • Signs of other preexisting diseases, such as diabetes or liver failure, which can cause ATN
• During history taking, the physician may request the following information:
  • When the symptoms began and whether they are becoming worse
  • List of prescription and over-the-counter medications currently being taken
  • About one’s personal and family history of kidney disease, diabetes mellitus, etc.
  • History of recent imaging procedures
• Consultation with a nephrologist may be necessary, as they are the experts in dealing with kidney disorders

When Acute Tubular Necrosis is suspected, the following diagnostic tests may be necessary to analyze the cause and monitor the condition:

• Blood urea nitrogen test: Serum creatinine ratio
• Creatinine clearance
• Level of electrolytes in blood, such as potassium, sodium, bicarbonate, magnesium, calcium, phosphate, etc.
• Urinalysis: A complete analysis of urine is essential, which also include urine sodium and urine osmolality. Urinalysis may show characteristic “muddy brown” color
• Fractional excretion of sodium (FENa)
• Blood gas analysis (ABG) to measure the level of oxygenation and any imbalance in the metabolic status of the body such as acidosis or alkalosis
• ECG (Electrocardiogram) may also be taken, especially to monitor electrolyte imbalances, which may cause abnormal rhythm in the heart and may likely become fatal
• Other tests, depending on the history and physical examination

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Acute Tubular Necrosis?

The complications of Acute Tubular Necrosis (ATN) may include:

• Chronic kidney disease (chronic renal failure or CRF): ATN can cause permanent damage, if the condition is not diagnosed promptly and treated appropriately
• Hypertension: In a patient with previously normal blood pressure, ATN can cause high blood pressure
• Infection, which can progress to septic shock
• Irregular heart beat (arrhythmia) can lead to sudden death

How is Acute Tubular Necrosis Treated?

Unlike other types of acute kidney injuries, Acute Tubular Necrosis is usually reversible with appropriate treatment, if there are no major associated diseases. The aim of the treatment is to prevent major complications from arising and the treatment plan should include treating the underlying disorders that triggered ATN.

• The mainstay of the treatment is fluid therapy and monitoring of fluid input and output
• To prevent the accumulation of ammonia and acid levels (metabolic acidosis) in the body, the individual may be placed on a low protein diet
• Diuretics may be needed sometimes to increase the urine output
• Plasma ultrafitration is a relatively new technique that may be used, when the individuals are non-responsive to diuretics
• Dosage of medications which the individual was previously on, may be adjusted based on the clinical situation
• Discontinuing medications that caused ATN such as Amphotericin B
• Certain medications may be given or avoided to prevent a buildup of toxic levels of substances, which may worsen renal failure

If the above treatment options are not effective in managing Acute Tubular Necrosis, dialysis may be performed to help the kidney recover quickly. This process is used for a short duration of time. The indications for dialysis include:

• Very high levels of potassium or other electrolytes that do not respond to medications
• Excess fluid in the body that do not respond to conservative measures
• High acid levels (metabolic acidosis) in the body and not responding to conservative measures
• No urine output despite the use of conservative measures
• Deterioration in mental status
• Pericarditis: Inflammation of the external protective layer of the heart

How can Acute Tubular Necrosis be Prevented?

The following measures may be considered to prevent the development of Acute Tubular Necrosis:

• In individuals, who may undergo any diagnostic testing that involve a dye (contrast), proper hydration (IV fluids or normal saline) should be maintained before the procedure, especially for those with diabetes mellitus, chronic kidney disease, heart failure, recent consumption of ACE inhibitors, NSAIDs, etc.
• Optimally, treating chronic conditions and complications, such as diabetes, liver disease, heart disease etc., which can likely cause ATN
• Anticipating kidney damage, when starting a new medication that has a tendency to cause ATN, and following up for the same with proper diagnostic evaluation
• Anticipating kidney damage, when individual has had a crush injury (due to an accident/trauma) and promptly treating the condition with a judicious use of intravenous fluids
• Medications, such as allopurinol, can be given before starting chemotherapy for cancers to avoid high levels of uric acid that can cause Acute Tubular Necrosis

What is the Prognosis of Acute Tubular Necrosis? (Outcomes/Resolutions)

• The prognosis of Acute Tubular Necrosis depends upon the severity at presentation and initiation of appropriate therapy. Nevertheless, unlike other acute kidney injuries or conditions, Acute Tubular Necrosis is usually reversible with appropriate treatment, if no major associated diseases are present
• Sufficient urine output ATN (non-oliguric) has more favorable prognosis in comparison to minimal urine output ATN (oliguric)
• The prognosis is not favorable if the condition requires intensive care monitoring (ICU)
• Other factors that are associated with unfavorable prognosis include older age, multiple organ failure, and advanced underlying medical conditions

Additional and Relevant Useful Information for Acute Tubular Necrosis:

• Acute kidney failure is a condition when the kidneys can no longer filter wastes out of blood. In this condition, there is an abrupt loss of kidney function that develops over a period of few days

The following article link will help you understand acute kidney failure:

http://www.dovemed.com/diseases-conditions/acute-kidney-failure/